I have a 98 S90 and can someone please explain everything there is to know about OBD 2 and what its function is for becuase i have no idea im kinda a newbie to this mess.
thanks ...

OBD2 system is essentially your computer system that if something goes wrong in your car, sets off the Check engine light. There is a "port" where the mechanic can plug in a hand held scanner to read codes and then diagnose what is wrong.

Here's a link: http://www.obdii.com/background.html

OK thanks this is in NO way any sort of chip tuning deal? and if so i know i wont gain much cause my car is N/A.

no....every car has OBD2 out there.

no....every car has OBD2 out there.

well obd-2 is typically 96 and up vehicles